If you were lucky enough to get a hoverboard in your Christmas stocking this holiday season, you may have some trouble getting it home.

More than 60 airlines have banned hoverboards from being taken on their flights—either as carry-on items or in checked luggage—because of concerns about the scooters’ lithium-ion batteries, which are potentially combustable.

Lithium-ion batteries power everything from laptops to smartphones to Teslas. But the large size of a hoverboard’s battery—and the fact that some knockoff hoverboards are made cheaply and without proper safeguards—makes it particularly vulnerable to overheating. Several news stories have reported incidents in which hoverboards caught fire or exploded, injuring their riders or damaging nearby property. Understandably, airlines aren’t willing to take the risk of an onboard explosion.

Airlines’ hoverboard bans aren’t sitting well with passengers, including actor Russell Crowe, who had hoped to take their self-balancing scooters with them on board.

Several airlines, including Southwest, appear to allow hoverboards in certain circumstances, although policies have been changing rapidly. (If you’ve got an upcoming flight, you should probably check with your airline directly.)

For their part, hoverboard makers have maintained that the scooters are safe, even as local news broadcasts have been headlined by stories of hoverboards that have caught on fire and the U.S. Consumer Product Safety Commission has recorded at least 70 complaints of hoverboard-related emergency room visits.

“I wouldn’t feel safe having my kids on a plane without knowing the devices were safe either,” John Soibatian, president of IO Hawk, a major hoverboard manufacturer, told CNN.

The CPSC is currently investigating the root cause of all of the hoverboard fires. In the meantime, it has issued tips for hoverboard fans, including only purchasing scooters that are certified by a national testing laboratory.